Hello Silvan,
I'm glad you were satisfied, I'm not.
You probably have a smaller camera than I do (size? weight?).
I screwed my new Nikon D7500 incl. zoom 18-200mm on tightly, suddenly the camera together with the mounting plate fell on the stone floor and remained damaged.
Camera and zoom together weigh almost 1300 grams, which is quite a bit less than the stated payload of 2 kg.
I would urgently recommend Rollei to reduce the payload to 1 kg, because the wobbly tripod cannot take more!
Regarding your question, I would cut an aluminium sheet or a vegetable cutting board (very stable plastic) to the desired size.
to the desired size and buy a tripod screw.
Be careful not to use a normal screw because the thread is not metric.